feat(web): marketing Button, Nav (with mobile menu) and Footer from Figma, test-first

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_014SdXCbrN5PtGExkpvMaMHx

web/src/marketing/Footer.tsx

@@ -0,0 +1,37 @@
+import Link from 'next/link';
+import { FOOTER_COLUMNS, TAGLINE } from './content.ts';
+
+export function Footer() {
+  return (
+    <footer className="footer">
+      <div className="footer-top">
+        <div className="footer-brand">
+          <p className="t-title-m">Wursor</p>
+          <p className="t-body-m footer-muted">{TAGLINE}</p>
+        </div>
+        <nav aria-label="Footer" className="footer-columns">
+          {FOOTER_COLUMNS.map((col) => (
+            <div key={col.heading} className="footer-column">
+              <h2 className="t-label-m">{col.heading}</h2>
+              <ul>
+                {col.items.map((item) => (
+                  <li key={item.label} className="t-body-m footer-muted">
+                    {item.href ? <Link href={item.href}>{item.label}</Link> : item.label}
+                  </li>
+                ))}
+              </ul>
+            </div>
+          ))}
+        </nav>
+      </div>
+      <div className="footer-bottom t-label-s">
+        <span className="footer-status">
+          <span className="dot" aria-hidden="true" /> All systems normal
+        </span>
+        <span className="footer-spacer" />
+        <span className="footer-muted">English</span>
+        <span className="footer-faint">© 2026 Wursor</span>
+      </div>
+    </footer>
+  );
+}